Combined Seal Head and Pump Intake for Electrical Submersible Pump

ABSTRACT

An electrical submersible well pump assembly has a motor containing a dielectric lubricant. A seal section is mounted to the motor for reducing pressure differential between the lubricant in the motor and the well bore fluid. The seal section has a head on an end opposite the motor. A pump assembly is mounted to the head of the seal section. An intake is located in the head of the seal section for drawing well bore fluid into the pump assembly.

FIELD OF THE INVENTION

This invention relates in general to electrical submersible well pumps, and in particular to connections between the seal section of the pump assembly and the pump.

BACKGROUND OF THE INVENTION

Electrical submersible well pumps are commonly used for hydrocarbon well production. A typical pump assembly has an electrical motor with a seal section or protector on its upper end. The motor is filled with a dielectric lubricant. The seal section has an equalizer in communication with that lubricant. The equalizer is also in fluid communication with the well bore fluid for equalizing the pressure of the lubricant to that of the well bore fluid. Typically the seal section will also have a thrust bearing for absorbing downward thrust from the pump.

The pumping assembly may comprise one or more pumps and optionally a gas separator. The pumps are rotary pumps driven by a shaft of the motor. They may be either progressing cavity pumps or they may be centrifugal pumps having a large number of stages, each stage having an impeller and a diffuser. If a gas separator is employed, typically it has a rotary gas separating component for separating gas from the well fluid prior to the well fluid entering the pump.

A different connector is required on the lower end of the pump depending upon whether the pump is to connect directly to a seal section or to another component of the pumping assembly, such as a gas separator or another pump. The connectors are not readily interchangeable between pumps, thus the manufacturer may be required to keep both types. The reason for having both types of pumps has to do with whether the connector has intake ports or not. If the pump is connecting to an upstream component such as another pump or a gas separator, its connector would not have intake ports in it. If connecting directly to the seal section, the connector would need intake ports.

As further explanation of the prior art and referring to FIG. 1, pump 31 is a centrifugal pump having a number of stages, each stage having an impeller 33 and a diffuser 35. Pump 31 has a connector 37 on its lower end for connecting to other components of the pumping assembly. Connector 37 has external threads 39 that connect to internal threads in the housing of pump 31. Connector 37 has a flange 41 on its lower end containing a pattern of holes 43, each for receiving a bolt 45. Connector 37 does not have any intake ports leading directly to the exterior for drawing in well bore fluid. The reason is that pump 31 is constructed to be a tandem pump or one for connection to a gas separator below it. In those instances, the intake ports would be in lower connector of the lower tandem pump or in the lower connector of the gas separator.

If the manufacturer wishes to use pump 31 without connecting it to an upstream component, such as another pump or gas separator, he can do so by connecting it to a separate intake housing 47. Intake housing 47 is a separate sub that has intake ports 49 for well fluid to pass inward and up to pump 31. Intake housing 47 has its own short shaft 51 mounted therein and which connects to pump shaft 53 by a coupling 55. A radial bearing 57 supports intale shaft 51 in housing 47. Radial bearing 57 does not form a seal. A coupling on the lower end of intake housing shaft 51 will connect it to a seal section shaft (not shown). Intake housing 47 has a radial flange 61 for bolting to the seal section (not shown). While combining pump 31 with intake housing 47 allows a manufacturer to use pump 31 either as a tandem pump or as a single pump without a gas separator, it requires extra expense because of intake housing 47.

FIG. 2 illustrates another prior art pump 63 having a pump shaft 65. A connector 67 has upper exterior threads 69 for engaging mating threads in the interior of the housing of pump 63. Connector 67 has intake ports 71 for drawing in well fluid to pump 63. Connector 67 also has radial bearings or bushings 73 for supporting shaft 65. Bearings 73 do not form a seal. A coupling 75 on the lower end of shaft 65 connects the shaft to the seal section shaft (not shown). Connector 67 also has a flange 77 for bolting directly to the seal section.

Pump 63 is operable only by connecting it directly to the seal section. It cannot be used as a tandem pump because of its intake ports 71. In addition, connectors 67 and 37 (FIG. 1) cannot be interchanged. Shaft 65 protrudes farther than shaft 53 (FIG. 1) because of the need for space for intake ports 71. Consequently, to avoid the expense of having to use a separate intake housing 47, an operator may choose to stock both types of pumps 31 and 63.

SUMMARY OF THE INVENTION

In this invention, the seal section between the motor and the pumping assembly has a head on its end with an intake. The intake draws well bore fluid into the pump. The pump assembly, whether it includes is a gas separator, multiple pumps, or a single pump, has a simple connector on its lower end without intake ports. Placing the intake in the head of the seal section allows a standard connector to be utilized on all of the pumps regardless of whether the pump is to be connected directly to the seal section or to an upstream component of the pumping assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded sectional view of one prior art type of pump connector and an intake sub.

FIG. 2 is a sectional view of another prior art type of pump connector.

FIG. 3 is a schematic view of an electrical submersible pumping assembly constructed in accordance with this invention.

FIG. 4A is an enlarged sectional view of a seal section head and a lower portion of the pump of the assembly of FIG. 3.

FIG. 4B is a sectional view of a central portion of the seal section of the assembly of FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 3, electrical submersible pumping assembly (ESP) 11 is shown suspended in a cased well 13. ESP assembly 11 includes a motor 15, which is normally located on the lower end of the assembly, but in some instances on an upper end. A seal section 17 connects to the upper end of motor 15. Seal section 17 equalizes the pressure of lubricant within motor 15 to that of the well fluid in the well.

Seal section 17 has a head 19 on its upper end. Head 19 forms a part of seal section 17 and has intake ports 21 for drawing well fluid into head 19. ESP 11 may include an optional gas separator 23, which connects to the upper end of seal section head 19. Gas separator 23 separates gas from the well fluid flowing into intake 21 and discharges the gas out the gas outlet 25. The liquid components flow upward to a pump 27 that connects to the upper end of gas separator 23. Pump 27 may be a centrifugal pump or another type of rotary pump, such as a progressing cavity pump. Pump 27 is suspended by a string of tubing 29 through which the pump discharges. Gas separator 23 is employed only if conditions merit; in many instances pump 27 would connect directly to seal section head 19. Another pump could optionally be connected to the upper end of pump 27 in a tandem arrangement.

Referring to FIG. 4A, pump 27 has a standard connector 79 on its lower end that is employed whether pump 27 connects directly to seal section 17, to another pump, or to gas separator 23 (FIG. 3). In FIG. 4A, pump 27 is shown being directly connected to head 19 of seal section 17. Connector 79 has exterior threads on its upper end that engage internal threads in the housing of pump 27. Connector 79 has a flange 83 with a bolt pattern 85. Connector 79 does not have intake ports to the exterior.

Seal section head 19 has a flange 87 on its upper end that has a bolt pattern 89 that mates with bolt pattern 85. Connector 79 thus attaches directly to seal section head 19, if desired. A lower portion of connector 79 inserts into seal section head 19 and is sealed to seal section head 19 by a seal 90. Seal section 17 has a cylindrical housing 91 with internal threads 93 at its upper end. Seal section head 19 has external threads 95 on a lower interior portion that extend into housing 91. Threads 95 mate with threads 93 to secure head 19 to seal section housing 91. A seal 97 seals head 19 to the interior of seal section housing 91.

Seal section head 19 has an axial passage 99 extending through it. Seal section 17 has a shaft 101 that extends through it. Shaft 101 extends upward through axial passage 99. A bushing 103 in passage 99 radially stabilizes shaft 101, but does not seal. A seal assembly 105 is located above bushing 103 for sealing shaft 101 to passage 99. Seal assembly 105 may be a variety of types and combinations of seals. In this type, it includes a rotating member that rotates with shaft 101 and is urged by a spring against a stationary member. Seal assembly 105 seals a cavity 107 in head 19 from a cavity 109 in the interior of seal section 17. Seal head cavity 107 is in fluid communication with well bore fluid because of intake ports 21. Cavity 109 is in fluid communication with lubricant of motor 15 (FIG. 3). Seal assembly 105 thus seals the lubricant from the well bore fluid.

Pump 27 has a pump shaft 111 that extends downward a short distance below connector 79. A coupling 113 connects pump shaft 111 to seal section shaft 101. Coupling 113 is located within seal head cavity 107.

Seal section 17 (FIG. 3) may be a variety of types and will normally have a thrust bearing (not shown) to absorb thrust imposed on its shaft 101 by pump 27. In one example, as illustrated in FIG. 4B, an equalizer bag 115 is located in housing 91. Bag 115 is an elastomeric flexible container that has its upper and lower ends sealed around a central tube 117. Tube 117 has ports 119 that communicate with an annular space between shaft 101 and tube 117. The annular space is in communication with lubricant in motor 15 (FIG. 3). Dotted lines in FIG. 4A illustrate schematically that central tube 117 extends upward to seal section head 19, where it attaches and seals to provide a flow path for lubricant from motor 15 (FIG. 3).

Equalizer bag 115 has well fluid on its exterior so that it will equalize or at least greatly reduce any pressure difference between the motor lubricant and the well bore fluid. In this embodiment, a port 121 extends downward from the exterior of head 19 to the interior of seal section housing 91 to deliver well fluid to the exterior of bag 115, as illustrated by the dotted lines in FIG. 4A. Other types of seal sections are feasible. In another type (not shown), the equalizer comprises a labyrinth chamber rather than a flexible bag. The labyrinth chamber has U-tubes arranged to allow the well fluid and lubricant to contact each other, but prevent the heavier well fluid from flowing upward through the U-tubes and back downward into the motor. Some seal sections may employ multiple bags; others may employ multiple labyrinth chambers; and others may employ a combination of the two.

In the operation of ESP 11, in one mode, pump 27 is connected directly to seal section head 19. When motor 15 is energized, well fluid will be drawn through intake ports 21 for being acted on by pump 27. Seal section 17 protects the lubricant in the motor from contamination by the well bore fluid. Seal section 17 also equalizes the pressure of the lubricant to that of the well bore fluid.

In another mode, as shown in FIG. 3, pump 27 with its connector 79 (FIG. 4A) would attach to the upper end of gas separator 23. Gas separator 23 in that instance could have a connector that is substantially the same as connector 79 for connecting to seal section head 19. The well fluid would flow into intake ports 21 of seal section head 19, then to gas separator 23. Pump 27 and its connector 79 could alternately be employed as an upper or middle tandem pump, in which case connector 79 would connect to the upper end of a lower pump, and the lower pump would connect to seal section head 19.

The invention has significant advantages. By placing the intake in the head of the seal section, connectors for the pumping assemblies may be standardized. The same pump could be used as a single, stand-alone pump, or one connected to a gas separator, or one connected to a lower tandem pump.

While the invention has been shown in only one of its forms, it should be apparent to those skilled in the art that it is not so limited but is susceptible to various changes without departing from the scope of the invention. 

1. An apparatus for pumping wellbore fluid, comprising: a motor containing a dielectric lubricant; a seal section mounted to the motor for reducing pressure differential between the lubricant in the motor and wellbore fluid; the seal section having a head on an end opposite the motor a pump assembly mounted to the head of the seal section; and an intake in the head of the seal section for drawing wellbore fluid into the pump assembly.
 2. The apparatus according to claim 1, wherein the head has a flange containing a bolt pattern for bolting the seal section to the pump assembly.
 3. The apparatus according to claim 1, wherein the seal section comprises: a tubular housing having a set of internal threads at one end of the housing; and wherein the head has a set of external threads that engage the internal threads in the housing to secure the head to the housing.
 4. The apparatus according to claim 1, wherein the seal section further comprises: a seal section shaft extending through the seal section and into the head.
 5. The apparatus according to claim 1, further comprising: a seal section shaft driven by the motor and extending through the seal section into the head; a pump shaft in the pump assembly; and a coupling within the head for coupling the seal section shaft to the pump shaft.
 6. The apparatus according to claim 1, further comprising: an axial passage in the head; a seal section shaft extending through the seal section and the axial passage of the head; and a seal sealing the seal section shaft in the passage, the seal having lubricant from the motor on one side and wellbore fluid from the intake on the other side.
 7. The apparatus according to claim 1, further comprising: a communication port in the seal section head extending from the exterior of the head to an interior portion of the seal section for communicating wellbore fluid to the seal section.
 8. The apparatus according to claim 1, further comprising: a flange with a bolt pattern on an end of the head; and a tubular connector on an end of the pump assembly, the connector having a flange with a bolt pattern that mates with the flange on the head to connect the seal section to the pump assembly.
 9. The apparatus according to claim 1, wherein the pump assembly comprises a rotary pump.
 10. The apparatus according to claim 1, wherein the pump assembly comprises a gas separator and a rotary pump.
 11. An apparatus for pumping wellbore fluid, comprising: a motor containing a dielectric lubricant; a seal section mounted to the motor, the seal section having a seal section shaft that is driven by the motor, the seal section having a housing containing an equalizer for reducing pressure differential between the lubricant in the motor and wellbore fluid; the seal section having a head on an end opposite the motor, the head having an interior portion that inserts into and secures to the seal section, the head having an exterior portion with a flange having a bolt pattern; a pump assembly having a pump shaft and a connector on one end with a flange and bolt pattern that mates with and is bolted to the flange on the head of the seal section; a coupling located within the head that couples the pump shaft to the seal section shaft; and an intake in the head of the seal section for drawing wellbore fluid into the pump assembly.
 12. The apparatus according to claim 11, wherein the interior portion of the adapter has external threads that engage internal threads in the housing of the seal section.
 13. The apparatus according to claim 11, further comprising: a communication port in the head, the port extending from an exterior of the head to an interior of the housing for communicating wellbore fluid to the equalizer.
 14. The apparatus according to claim 11, further comprising: an axial passage in the head through which the seal section shaft extends; and a seal sealing the seal section shaft in the passage, the seal having lubricant from the motor on one side and wellbore fluid from the intake on the other side.
 15. The apparatus according to claim 11, wherein the pump assembly comprises a rotary pump.
 16. The apparatus according to claim 11, wherein the pump assembly comprises a gas separator and a rotary pump.
 17. A seal section for an electrical submersible well pump assembly, comprising: a seal section housing having a motor end for coupling to an electrical motor containing a dielectric lubricant and an intake end opposite the motor end and having a set of internal threads; a pressure equalizer located in the housing for reducing a pressure differential of the lubricant and wellbore pressure; a seal section head having an internal portion that extends into the housing with external threads that engage the internal threads in the housing, the seal section head having an external portion protruding from the housing and having an annular flange with a bolt pattern for bolting to a component of the pump assembly; a shaft extending through the housing and sealingly into the seal section head; and an intake port in the seal section head for delivering wellbore fluid to a pump of the pump assembly.
 18. The seal section according to claim 17, further comprising: a communication port extending through the seal section head from an exterior portion of the seal section head for communicating wellbore fluid to the pressure equalizer.
 19. The seal section according to claim 17, further comprising: a shaft passage extending through the seal section head through which the shaft extends; and a shaft seal in the shaft passage for sealing around the shaft, the shaft seal sealing lubricant within the equalizer of the seal section from wellbore fluid in the intake. 